• PDF / 437,539 Bytes
• 9 Pages / 547.087 x 737.008 pts Page_size
• 79 Downloads / 238 Views

DOWNLOAD

REPORT

---

Finite element evaluation of residual stresses in thick plates Alireza Chaboki Khiabani Æ S. A. Sadrnejad

Received: 24 September 2008 / Accepted: 12 February 2009 / Published online: 28 February 2009
Springer Science+Business Media, B.V. 2009

Abstract This paper makes use of the Finite Elements Method (FEM) to study and analyze residual stresses in the cold bending and welding of thick plates. The welding model consists of two steps: first, performing of the thermal transient analysis model; and second, the carrying out of the mechanical transient analysis based on the temperature pattern at each node on each particular time. Used in these models is the inelastic temperature-dependent material. The output of the model includes residual stresses and permanent distortion; these were then compared with verified experimental results. The validated model and the results exhibit satisfactory agreement up to a 15-percent difference. As for the cold bending of thick plates, it is modeled using another finite element model and the residual stresses and permanent curvature of the thick plates are computed numerically. Again, the FEM model was validated against some official experimental results and satisfactory agreement between them was observed. Finally, the effects of these two different sources of residual stresses were combined, the combined effects established, and the results then discussed.

A. C. Khiabani (&) Department of Engineering, University of Kurdistan, Sanandaj, Iran e-mail: [email protected] S. A. Sadrnejad Department of Civil Engineering, University of K.N.T, Tehran, Iran e-mail: [email protected]

Keywords Residual stresses
Cold bending
Welding
FEM
Thick plate

1 Introduction With fabrication processes of steel structures, including cold bending/forming and welding, said structures experience inhomogeneous plastic deformation that results in the development of residual stresses; the magnitudes of which often extend up to the yield strength and their distribution complicated in all dimensions. When in combination with operation/ service stresses, they give rise to a complex stress state acting on in-service condition. This paper focuses on cold bending and welding processes with their induced residual stresses derived numerically using the Finite Element method (FEM). One of the major sources of residual stress in the manufacturing process is cold bending. Cold roll bending is a metal forming process that is commonly used and one can find end products in numerous applications like buildings, vehicles and airplanes. Since trial and error can prove costly when designing a curved plate especially that of two or three dimensions, an alternative would be to use FE-analyses to investigate the strain and stress in a formed profile and to predict induced residual stress. The result from the simulations can be used to make better, safer and more economical the design of structures. It must be mentioned that with this process, the moment that

123

254

exceeds yield moment causes yield strain in the